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the 
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oti^ 
fin 
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or 


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shi 

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dif 
eni 
bej 
rig 
rec 
m« 


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method: 


Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microffiche,  selon  le 
cas:  le  symbols  —►  signifie  "A  SUIVRE",  le 
symbols  y  signifie  "FIN  ". 

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de  Tangle  supirieur  gauche,  de  gauche  d  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  ndcessaire.  Les  diagrammes  suivants 
illustrent  la  m6thode. 


1 

2 

3 

1 

2 

3 

4 

5 

6 

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BULLETIN   OF  THE  GEOLOGICAL   SOCIETY   OF  AMERICA 
Vol.  10,  pp.  193-198,  pl.  2t 


b  v^. 


'M 


/ 


iiLACIAL  PHENOMENA  IN  THE  CANADIAN  YUKON  DISTRICT 


BY 


J.  B.  TYRRELL 


M 


ROCHESTER 

PUBLISHED  BY  THE  SOCIETY 

April,  1899 


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BULL.   GEOL.   SOC.   AM. 


VOL.   10,    189H,   PI  . 


GLACl 


Introdn 

Area  trii 

I'livKioj? 

(ilacial  1 

Kxt 

The 

8tri 

Mo) 

Ten 


Int 


Tiast 
Houthw 
ern  par 
for  ohs 
occur  t 
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deep  ai 


My  r 
what  is 
the  Chi 
or  Chil( 
being  oc 

XXI 


CANADIAN   YUKON   DISTRICT 


iH.  PI  .  ;m 


bi> 


BULLETIN  OF  THE  GEOLOGICAL  SOCIETY  OF  AMERICA 

Vol.  10,  pp.  193-198,  PL.  21  April  3,  1899 


GLACIAL  PHENOMENA  IN  THE  CANADIAN  YUKON  DISTRICT 


'64 


-63 


-62 


BY    ,r.    H.    TYHHELT. 

{Raid  before  the  Sociclj/  December  SO,  JS.'>S) 

CONTENTS 

Introduction ]();> 

A roa  tru versed !<);{ 

I'liyKiof,'raj)liic  feiituroK 194 

(ilacial  features 105 

Kxtent  of  the  snow  and  ice 1!),") 

Tiie  till '  195 

iStriation I9(; 

Moraines 19(1 

Terrace.s 197 

Tlie  classes 1 97 

Stream  terraces 197 

Lake  terraces 197 

In  tlie  Dawson  district .. .    198 


-60 


-59 


IXTRODUCTrON 

Last  .suiniuer,  while  traveling  on  ]i()rsel)aek  and  on  foot  througli  the 
Houthwestern  ]>ortion  of  the  Yukon  district  and  the  extreme  nortliwest- 
ern  parts  of  British  Columbia,  many  opportunities  presented  them.selves 
for  observing  glacial  i)henomena-  oi)portunities  such  as  would  hardly 
occur  to  those  wlio  were  i)assing  through  tlie  same  country  in  boats  on 
some  of  the  many  streams  which  flow  along  the  bottoms  of  the  many 
deep  and  wide  valleys. 

Area  Travkrskd 

My  route  lay  to  .the  west  of  the  Lewis  river,  on  antl  in  the  vicinity  of 
what  is  generally  knoAvn  as  the  Dalton  trail — tliat  is,  up  the  valleys  of 
the  Chilcat  and  Klaliina  or  Tleliini  rivers,  over  the  summit  of  the  Coast 
or  Chilcat  range,  and  down  a  wide  and  continuous  valley  which,  after 
being  occupied  in  succession  by  parts  of  several  streams,  forks,  the  easterly 

XXIX-Bui.!,.  Okoi..  Soc.  Aji.,  Vol.  10,  I8»8  (193) 


II 


! 

I 


lUl        ,1.    i!.    I'YUK'KI.I, — (il.At  lAI.    1'III:N(».MI:NA     in     YIKON    DISI'K  l( 'I' 

jxirtion  lonninif  the  Viillcy  of  the  N()i'(U'ii>ki(tl(l  river,  which  joins  the 
Vul<i)M  a  short  distance  ahove  Kive-tinucrs  rapids,  while  the  westerly 
vaUcv  j>asses  northward  l»y  Aishihik  lake  to  Nislinj:  river,  down  tlmt 
rivt-r  to  White  river,  and  thence  down  tin-  White  to  the  point  where  it 
tlows  into  th(^  Yukon  river. 

In  addition  to  tlie  trip  outlined,  a  short  time  was  spent  farther  north 
on  the  Klondike  river  and  its  trihutaries. 


N 


I'nVsKKiKAIMlIC    FKArrUKS 

'I'oward  tlu;  south  this  country  is  a  mass  of  st<n'p.  rocky,  unj^ruded 
mountains,  anionj^which  tower  the  uiant  peaks  of  Hulil)ard,  Vanctiuver, 
FiOijan,  and  Saint  l^lias.  'I'liese  mountains  lie  to  the  westward  of  the 
Uroat  valley  of  the  I.ynu  canal  and  ChiU'at  river,  and  form  a  ran,u,e  which 
would  appear  to  he  (piite  distinct  from  tlu^u'ranitic  "  Coast  ran^e,"  which 
forms  tlu!  western  wall  of  the  continent  fartlu'r  south,  in  hoth  Alaska 
and  British  Columhia.  In  order  to  distinguish  this  ranjic  more  clearly, 
I  propose  for  it  thenanu;  ■'('hilcat  ranije,"  associating  it  with  one  of  the 
most  powerful  ti'il>es  of  Indians  on  the  .Maskan  coast. 

'riiis  ranife  is  hounded  on  the  south  and  southwest  hy  the  I'aeilic 
ocean  and  toward  tin;  nortli  and  northeast  l)y  the  j;reat  t'hihiat-Alsek 
valley,  which  extends  inland  from  the  western  arm  of  the  fjynn  canal, 
lollowint?  more  or  less  closely  the  line  of  contact  of  the  granite  to  the 
northeast  and  tlu!  schists  and  limestones  to  the  soutliwcst.  'I'he  aver- 
aire  widtli  of  the  range  is  Ix'tween  SO  and  KHi  miles. 

Much  of  the  range  is  hurled  in  extensive  snowlields.  from  which  gla- 
ciers radiate  in  all  directions,  ])oth  toward  tiie  coast  and  toward  the  in- 
terior. A  magnificent  view  of  this  country  was  obtained  last  siunnier 
from  thesuniinit  of  Farview  mountain,  a  high  peak  southwest  of  Aishihik 
lake,  and  itpresente<l  theai>pearance  of  a  vast  white  plain,  througli  which 
the  higher  peaks  rose  in  dark  relief,  mount  Saint  FLias  appciaring  for  a 
few  moments  from  beneath  the  clouds.  It  is  thus  a  vast  snow-clad  pla- 
teau, lying  close  to  tlu;  Pacific  coast,  in  one  of  the  regions  of  greatest 
precipitation  on  the  American  continent. 

Farther  north  the  country  is  also  mountainous,  hut  the  mountains  are 
much  more  rounded,  tli<>ir  slopes  are  easiiM-.  and  their  sides  show  com- 
parativeh'  few  broken,  ungraded  dill's.  .\s  a  rule,  they  rise  from  ;!,0()(l 
to  4,000  feet  above  the  bottoms  of  the  deeper  interveniijg  valleys.  Stand- 
ing on  one  of  the  summits,  a  great  numlier  of  similar  mountains  may  be 
seen  on  every  side,  all  about  the  same  height  and  prol)ably  cut  out  oi 
the  same  extensive  pre-Tertiary  i)eneplain. 

Lakes,  In  some  cases  of  large  size,  lie  in  the  l)ottoms  of  the  valleys  ; 


,,.,. 


ins  iiic 
•<'stcriy 
■n   Hint 

lirrc    it 


l'IIVSl()(ii;.\l'lllC    AM)    (il,.\(  lAI,    I'KA'l'lKKS 


lit." 


I»ut,  MS  fiir  MS  my  obscrvMlioiis  went,  tlicy  mik  (•(•nllncd  exclusively  to 
tliusc  parts  (»r  the  (MMiiitry  wliicli  Iimvc  Ween  inoro  or  less  coniplelely 
covered  l>y  ^^laciers  during'  tin;  IMeistocene  eiioeli.  Ueyond  the  limits  ol' 
the  ghiciiited  region  no  lake.s  were  seen. 

(iLAciAi,  Kkatiiui;s  • 

KXTI'XT  OF   THE  S^(lW  AM)   UK 

While  the  ChilcMt  mountains  are  almost  liiiried  in  snow  throutrhonl 
the  year,  very  little  snow  is  to  l)e  seen  in  summer  on  this  "  int(;rior  pla- 
teau," and  any  small  glaciers  that  do  exist  are  in  some  of  the  higher 
mountains  close  to  the  Chileat  range. 

Though  the  iee-tields  of  the  present  (Imv  are  eoidliied  almost  entiri'ly 
to  the  Chileat  mountMins,  the  iee-lields  of  the  (ilneial  per'  xl  were  much 
more  e.xtensive,  for  they  sprea<l  iiorthwMrd  as  far  ms  Kive-iingers  rapids 
on  the  T^ewis  river  and  to  a  short  distance  beyond  Aishihik  lake  in  the 
.Vishihik  valley.  TIk;  northern  limit  of  glaciation  is  not  hy  any  means 
an  approximately  straight  line,  for  it  indicates  the  lengths  to  which  the 
glaciers  tilled  tln^  valleys  rather  than  the  even  margin  of  a  great  conflu- 
ent ice-sheet.  The  higlier  mountains  rose  above  the  level  of  the  ice,  just 
as  they  do  at  the  jtresent  time  in  the  Chileat  range,  and  small  glaciers 
moved  down  their  sides  to  join  the  larger  glaciers  in  the  valleys. 

The  Chilcat-Alsek  valley  gives  a  beautiful  idea  of  the  former  depth  or 
thieknetJS  of  the  ice.  The  bottom  of  the  valley  is  almost  Hat,  and  the 
sides  rise  in  gentle  willow-covered  slopes  for  2,(M)()  feet  or  more  to  the 
foot  of  the  ungraded  rocky  peaks  on  either  hand,  liock  is  everywhere 
exposed  al)ovethis  line,wlHle  below  it  rock  exposures  are  comj)aratively 
rare,  and  the  country  is  underlain  by  a  loose  una.ssorted  till,  on  which 
willows  and  dwarf  birches  grow  in  dense  tliiekets.  As  seen  from  the 
bottom  of  th(!  valley,  the  upper  limit  of  the  willow-covered  sloi)e  forms 
a  fairly  regular  line  along  the  sides  of  the  mountains,  and  indicates  ap- 
proximately the  depth  to  which  the  ice-i-heet  filled  the  vallc}',  a  depth 
which  here  varied  from  2,000  to  3,000  feet.  Above  this  line  the  higher 
mountains  rise  in  broken,  jagged  peaks,  while  any  lower  mountains 
which  do  not  rise  above  the  level  of  the  toj)  of  the  till  have  their  .sum- 
mits evenly  rounded  and  unbroken. 


1     ■    "''rii 


.tin 


k 


THE   Till 


The  till  which  fills  the  bottom  of  this  valley,  often  to  depths  of  100 
feet  or  more,  is  a  mass  of  unassorted  material,  in  part  local  and  in  ])art 
derived   from   a  distance.     It   contains  pebbles  and  boulders,  usually 


190 


TYIilli;!.!, — (.|,A<  lAI,    I'MKNoMIA  A     IN     VI   KON     I  >l.sll{  It   T 


more  or  loMM  rounded  in  sliMpc.  some  of  wliicli  i\r«'  strint«'d  while  the 
greiil  niiijority  iire  sniootii  iind  without  ^diu-iid  iiuirkin^'s.  In  ;;ener;il 
chanii'ter  it  is  very  similur  to  tlie  till  which  underlies  so  niueh  (»!'  the 
|tl;iins  ol"  northwestern  ('aiiiula  lietweeii  the  edue  of  the?  Andiean  nueleiis 
and  th(!  IJoeky  mountains.  Similar  till  was  found  It)  undeilic!  the  hottoms 
anti  siiles  of  mt)st  of  the  valleys  everywhere  thrt)Ujrhout  the  j;lat'iateil 
area  in  tht^  Yukon  distriet,  havinjj;  evitleiitly  heeii  formeil  as  a  ground 
mt»raine  heneath  the  yfreat  sheets  of  iee. 


v 


,s/7i'/.l77o.V 

Striat(!tl  roek  surfaees  were  in/l  very  t)ften  st'en,  for  wluM'e  the  rt)ek  is 
exposetl  't  has  usually  heeome  rt)U,u;li  thrt)U,<;h  weatheriiijx,  hut  they  were 
re{'t)<!;nized  in  a  few  ])hiees  tin  the  interior  |tlateau,  anil  in  every  instance 
they  indicated  ailirectioii  t>f  ice-movenient  motion  from  tlu'  coast  tt»wartl 
the  interior  t)r  essentially  simply  a  wider  extension  of  the  ti,lacial  eon- 
ditioUH  which  exist  in  the  region  at  the  present  time,  in  this  extension 
toward  the  interit)r  tlu!  ice  for  the  mtist  part  ft)llt)wetl  the  ^n^at  valleys 
which  trench  tlu;  surface  t)f  the  country  in  a  <reueral  nt)rth-and-south 
directit)u,  and  therefore  the  mt)vement  of  the  ice  was  generally  north- 
wanl. 

Close  to  the  coast  the  Lilaciers  tli)Wed  seawanl  anti  lilletl  the  many 
deep  valleys  which  tlesceml  l'rt)m  the  mttuntains  tt>  the  I'acilic  ocean. 
In  the  Skagway  valley  the  White  I'ass  railrt)ail  while  constructiutr  it.« 
line  has  cut  a  nt)tch  along  a  rocky  hillside  which  has  heen  heautifully 
.smoothetl  and  scoretl  hy  such  a  glacier. 


• 


■:  i 


MO  HA  I  Mis 

Lateral  moraines  occasionally  form  ct)nspicuous  features  along  the 
siiles  of  the  mountains,  often  runinng  as  long,  narrow  lines  of  hoidtlers 
or  transportetl  material,  swaying  slightly  up  ami  ilown  with  the  irregu- 
larities of  the  surface,  ami  in  jilaces  runiung  into  water-worn  terraces 
whert^  some  small  stream  has  thrown  its  loatl  of  gravel  against  the  side 
of  the  glacier.  A  very  well  marketl  moraim;  of  this  character  extends 
along  the  west  side  of  the  valley  of  .\ishihik  lake  at  ahout  1,.')()()  feet 
ahove  the  wat(;r.  It  is  a  fairly  regular  ridge  of  houlders,  along  the  crest 
of  wliich,  ill  some  places,  runs  the  horse  trail  from  Fort  Selkirk  south- 
ward to  Pyramid  harhor.  Ahove  it  the  surface  of  the  mountain  con 
sists  of  a  fairly  even,  regular  incline  of  deco!ni»osed  rock,  while  helow 
it  is  a.  till-coveretl  slope,  often  hroken  into  very  lumpy,  irregular  hills. 
Lateral  moraines  were  also  traced  down  the  side  of  a  deep  valley  iiorlii- 
west  of  Aisluhik  lake  as  well  us  in  some  other  places. 


.\|(>i;aini:s   and  tkI!I!A(i:s  |'.»7 

'I'criiiiiiiil  inoniiiii's  wtTf  rccogiiizi'd  in  m  lew  plMccs,  hut  they  sciircfly 
torincd  iih  ('()iis|iicii(»us  fciilurcs  as  one  would  luivc  liecii  incliiit'd  to  ex- 
pect. Krom  lake  Aisliili'k  iiortliwiird  for  mImmU  I'-'  nnles  in  the  liottoui 
of  the  vMJh'V  is  m  tei'MiinMl  nioraiiu'  areii,  rt'|ireseiit<'d  in  places  l)y  irreg- 
ular hills  of  houlders,  which  was  l'ornu;d  at  the  foot  of  the' Aishihik  lolx; 
of  tlu;  ji;reat  icie-sheet  wlieii   it  had  reacheil   its  cxtreii  .   uortheni  limit. 


'/•/•'A- A' .If  ■/•;>■ 

T/ic  fhisst's. — -'riie  terraces  occurrin<f  in  this  n^gion  are  of  two  kinds, 
UJinit'l}',  ulrrniii  tcrrttccx  and  htkc  tcrniccx. 

Strciim  tcrvdcci^. — Stream  terraces  have  cliielly  Iteen  formed  hy  torrential 
rivers,  loaded  with  detritus,  ilowiuLi;  from  the  feet  of  the  ;j;laciers,  and  are 
most  conspicuous  in  the  larger  valh-ys  heyond  the  limits  of  the  glaciated 
area,  as,  for  instance,  in  the  valleys  of  licwisand  Nislin^  rivers  ;  Itutastlu? 
jflaciers  diminished  in  size  and  their  fronts  retired  U])  the  valleys,  gravel.s 
and  sands  were  deposited  in  the  hottoms  of  the  valleys  wliich  had  i)re- 
viously  heen  occupied  h}'  the  ice,  and  thus  terraces  wore  formed  on  the 
low  lands  in  the  region  which  had  been  covered  with  glaciers. 

Lake  terraces. — Ivake  terraces  are  confined  exclusively  to  the  glaciated 
area,  none  having  been  recognized  beyond  the  northern  limits  to  which 
the  vast  ice-sheets  of  theCJlacial  period  e.xtended.  'I'hey  usually  consist  of 
fine  sand,  silt,  or  rock  (lour,  which  is  often  of  whitish  color  and  commonly 
has  the  apjiea ranee  of  the  tincr  material  carried  down  intol)0(lies  of  <|uiet 
water  hy  glacial  streams.  Theses  terraces  sometimes  extend  li,Ot)0  feet  or 
more  up  tlie  .sides  of  the  mountains,  especially  in  wider  parts  of  some  of 
the  great  valleys  which  traverse  the  country.  Such  terraces  are  beauti- 
fully shown  on  the  sides  of  the  mountains  around  lake  Dezedeash. 
'I'lien;  can  be  no  doubt  that  the  outlets  to  the  valley  were  tilled  with  ice, 
and  that  the  deep  lake  which  existed  here,  around  the  shores  of  which 
the  terraces  of  white  silt  were  formed,  was  in  part  walled  in  by  the  fronts 
of  glaciers. 

Sinnlar  terraces  were  seen  in  nuiny  other  places,  and  often  several 
would  descend  in  regular  series,  until  it  was  diflicult  to  distinguish  the 
lowest  from  the  higher  and  finer  of  the  stream  terraces.  It  is  confidently 
believed,  however,  that  all  the  white  silt  terraces  in  that  portion  of  the 
Yukon  district  examined  were  formed  in  ice-dammed  lakes  and  furnisli 


f  I 


i '  ■i>,'<i 


,    Si 


1 


•>  t.: 


m 


lOS       J.  IJ.  TYKRKLL — fiLACIAf,    IMIICNOMKXA    IN    Vr'KON    DISTHK'T 

no  evidence  whatever  of  marine  conditions  or  of  recent  submergence  of 
the  land.  Any  regularity  in  heij?ht  of  the  highest  terraces  is  easily  ac- 
counted for  by  the  moderately  regular  average  thickness  of  the  ice-sheet 
when  the  lakes  were  in  existence. 


IN  THE  DAWSOy  DlHTlilCT 

As  small  glaciers  now  exist  in  the  valleys  of  the  mountains  north  of 
the  Chilcat  range,  so  small  glaciers  formerly  existed  in  some  of  the 
mountain  valleys  north  of  the  main  ice-sheet  of  the  Glacial  period. 
Such  glaciers  existed  in  the  valleys  of  Eldorado  and  Bonanza  creeks, 
near  Dawson,  and  flowed  down  these  valleys  at  least  to  some  point  below 
the  confluence  of  the  two  creeks.  Beautiful  glacial  stria«  were  seen  on 
the  hard  quartzose  rocks  at  the  mouth  of  Big  Skookum  gulch,  on  the  west 
side  of  Bonanza  creek,  which  had  been  made  by  this  glacier,  furnishing 
indisputable  evidence  of  its  presence.  A  lateral  moraine  of  this  glacier, 
often  containing  pebldes  and  small  boulders  of  distinct  glacial  shapes, 
extends  along  the  side  of  the  valley  from  150  to  200  feet  above  the  creek, 
and  in  it  are  some  of  the  rich  bench  claims  on  Eldorado  hill  and  at 
French  gulch,  and  the  sand  and  gravel  in  the  bottom  of  the  valley  is 
well  rounded,  but  roughly  assorted  material,  such  as  is  constantly 
washed  down  and  distributed  by  glacial  streams. 


I 


